Without limiting the scope of the invention, its background is described in connection with a fluoroluminescence sensor using a coated article, such as a fiber optic cable, that is immersed in a sample solution.
The use of fluorescence based technology to detect sample gases and liquids has been known for some time now. A typical application involves the molecular labeling of a thin film, cable or other article followed by excitation and fluorescent measurement in the presence of the particular sample of interest. Fluorescent labeling involves the deposit of a suitable fluorescence chemistry known to interact with the sample of interest. A source of excitation light is directed at the coated article which when brought in contact with the sample emits a low intensity fluorescence energy. A light detector can be used to measure the emission and detect the presence of the sample. These processes can also be modified to work on solids.
A known prior art system uses a fluorescence-based fiber optic oxygen sensor with a single high brightness Light Emitting Diode (LED). A signal generator and LED are used to generate the excitation signal that is first guided through a filter and then through a coated and unclad fiber optic cable mounted in a gas flow cell. Escaping light excites the coated dye on the cable which, in turn, emits a certain intensity of light related to the concentration of the oxygen sample. The emitted light is then directed through a second filter and to a light detector via a collecting lens. The output of the detector is amplified and read out on an instrument.
The signal generator, LED, lens, filter, detector, amplifier and other components of prior art sensor systems require a significant amount of space and, as such, are typically reserved for the laboratory or research facility. Such systems require special mounting apparatuses, are expensive to build and maintain and cannot be used in most field applications. Moreover, the detecting capability of such systems depends primarily on the amount of emission light which eventually reaches the detector. Light losses, however, are experienced with each stage of the setup placing a premium on the strength of the light source as well as the sensitivity of the detector. Also, the overall bulkiness and high number of components limits their use in most practical field applications. From a manufacturing standpoint, the prior art systems are expensive to build.